a motor has an electrical input of 30 kj and is used to raise 100 kg load to a height of 25m when fitted to a crane winch . what is the efficiency of winch?
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ist motor power is calculated by:
P = M.g.v/nM = Massg = Gravityv = velocity of raise mptionn (meant to be the greek letter nu) = efficiency losses due to gears/ pulleys
The standards applicable are BS466 (Electrical) and BS2573 (Pt 1 and 2 - Mechanical). All the info provided in earlier answers covers this. Dimensionally, this works out as P (Watts, or Joules/sec, or Force*velocity) in kg.m2s-3
I personally think (this is not really a 'personal; opinion, I'm a crane engineer) it's best to look at the force delivering a given velocity of lift, as this is principally what the designer is after..the mass bing lifted against gravity as the the force element (Newtons), and the power being accordingly calculated as the speed the load is to be lifted at (Velocity).
There is a whole other piece of thinking to understand Pull out torque - this is given in BS466 as 'at leat 225% more than the torque required to lift the load at the required design speed'. Looking at Slip (Rotational speed)/ torque curves should note that the hoist motor will be selected to work at >=96% slip at the max load. This isn't obvious from the calc' the speed/torque curve for a given motor should be obtainable from the manufacturer of the hoist motor. Lower loads mean the hoist will rotate slightly faster (noting it will be synchronous, or zero slip = 100% rotational speed at no load - the weight of the hook block means there always s some load, which is known as 'Light Hook' -so in practice there will always be some slip).
Apologies to labour the point, t
P = M.g.v/nM = Massg = Gravityv = velocity of raise mptionn (meant to be the greek letter nu) = efficiency losses due to gears/ pulleys
The standards applicable are BS466 (Electrical) and BS2573 (Pt 1 and 2 - Mechanical). All the info provided in earlier answers covers this. Dimensionally, this works out as P (Watts, or Joules/sec, or Force*velocity) in kg.m2s-3
I personally think (this is not really a 'personal; opinion, I'm a crane engineer) it's best to look at the force delivering a given velocity of lift, as this is principally what the designer is after..the mass bing lifted against gravity as the the force element (Newtons), and the power being accordingly calculated as the speed the load is to be lifted at (Velocity).
There is a whole other piece of thinking to understand Pull out torque - this is given in BS466 as 'at leat 225% more than the torque required to lift the load at the required design speed'. Looking at Slip (Rotational speed)/ torque curves should note that the hoist motor will be selected to work at >=96% slip at the max load. This isn't obvious from the calc' the speed/torque curve for a given motor should be obtainable from the manufacturer of the hoist motor. Lower loads mean the hoist will rotate slightly faster (noting it will be synchronous, or zero slip = 100% rotational speed at no load - the weight of the hook block means there always s some load, which is known as 'Light Hook' -so in practice there will always be some slip).
Apologies to labour the point, t
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